Create both atomic16_read_ro and atomic16_read_rw.
Previously we pretended that we had atomic16_read in system mode,
because we "know" that all ram is always writable to the host.
Now, expose read-only and read-write versions all of the time.
For aarch64, do not fall back to __atomic_read_16 even if
supported by the compiler, to work around a clang bug.
Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
---
host/include/aarch64/host/atomic128-ldst.h | 21 ++++++++-------
host/include/generic/host/atomic128-ldst.h | 31 ++++++++++++++++------
target/s390x/tcg/mem_helper.c | 2 +-
3 files changed, 36 insertions(+), 18 deletions(-)
diff --git a/host/include/aarch64/host/atomic128-ldst.h
b/host/include/aarch64/host/atomic128-ldst.h
index c2e7b44bc5..6959b2bd8e 100644
--- a/host/include/aarch64/host/atomic128-ldst.h
+++ b/host/include/aarch64/host/atomic128-ldst.h
@@ -11,10 +11,18 @@
#ifndef AARCH64_ATOMIC128_LDST_H
#define AARCH64_ATOMIC128_LDST_H
-/* Through gcc 10, aarch64 has no support for 128-bit atomics. */
-#if !defined(CONFIG_ATOMIC128) && !defined(CONFIG_USER_ONLY)
-/* We can do better than cmpxchg for AArch64. */
-static inline Int128 atomic16_read(Int128 *ptr)
+/*
+ * Through gcc 10, aarch64 has no support for 128-bit atomics.
+ * Through clang 16, without -march=armv8.4-a, __atomic_load_16
+ * is incorrectly expanded to a read-write operation.
+ */
+
+#define HAVE_ATOMIC128_RO 0
+#define HAVE_ATOMIC128_RW 1
+
+Int128 QEMU_ERROR("unsupported atomic") atomic16_read_ro(const Int128 *ptr);
+
+static inline Int128 atomic16_read_rw(Int128 *ptr)
{
uint64_t l, h;
uint32_t tmp;
@@ -41,9 +49,4 @@ static inline void atomic16_set(Int128 *ptr, Int128 val)
: [l] "r"(l), [h] "r"(h));
}
-# define HAVE_ATOMIC128 1
-#else
-#include "host/include/generic/host/atomic128-ldst.h"
-#endif
-
#endif /* AARCH64_ATOMIC128_LDST_H */
diff --git a/host/include/generic/host/atomic128-ldst.h
b/host/include/generic/host/atomic128-ldst.h
index 06a62e9dd0..79d208b7a4 100644
--- a/host/include/generic/host/atomic128-ldst.h
+++ b/host/include/generic/host/atomic128-ldst.h
@@ -12,16 +12,25 @@
#define HOST_ATOMIC128_LDST_H
#if defined(CONFIG_ATOMIC128)
+# define HAVE_ATOMIC128_RO 1
+# define HAVE_ATOMIC128_RW 1
+
static inline Int128 ATTRIBUTE_ATOMIC128_OPT
-atomic16_read(Int128 *ptr)
+atomic16_read_ro(const Int128 *ptr)
{
- __int128_t *ptr_align = __builtin_assume_aligned(ptr, 16);
+ const __int128_t *ptr_align = __builtin_assume_aligned(ptr, 16);
Int128Alias r;
r.i = qatomic_read__nocheck(ptr_align);
return r.s;
}
+static inline Int128 ATTRIBUTE_ATOMIC128_OPT
+atomic16_read_rw(Int128 *ptr)
+{
+ return atomic16_read_ro(ptr);
+}
+
static inline void ATTRIBUTE_ATOMIC128_OPT
atomic16_set(Int128 *ptr, Int128 val)
{
@@ -32,10 +41,14 @@ atomic16_set(Int128 *ptr, Int128 val)
qatomic_set__nocheck(ptr_align, v.i);
}
-# define HAVE_ATOMIC128 1
-#elif defined(CONFIG_CMPXCHG128) && !defined(CONFIG_USER_ONLY)
+#elif defined(CONFIG_CMPXCHG128)
+# define HAVE_ATOMIC128_RO 0
+# define HAVE_ATOMIC128_RW 1
+
+Int128 QEMU_ERROR("unsupported atomic") atomic16_read_ro(const Int128 *ptr);
+
static inline Int128 ATTRIBUTE_ATOMIC128_OPT
-atomic16_read(Int128 *ptr)
+atomic16_read_rw(Int128 *ptr)
{
/* Maybe replace 0 with 0, returning the old value. */
Int128 z = int128_make64(0);
@@ -52,12 +65,14 @@ atomic16_set(Int128 *ptr, Int128 val)
} while (int128_ne(old, cmp));
}
-# define HAVE_ATOMIC128 1
#else
+# define HAVE_ATOMIC128_RO 0
+# define HAVE_ATOMIC128_RW 0
+
/* Fallback definitions that must be optimized away, or error. */
-Int128 QEMU_ERROR("unsupported atomic") atomic16_read(Int128 *ptr);
+Int128 QEMU_ERROR("unsupported atomic") atomic16_read_ro(const Int128 *ptr);
+Int128 QEMU_ERROR("unsupported atomic") atomic16_read_rw(Int128 *ptr);
void QEMU_ERROR("unsupported atomic") atomic16_set(Int128 *ptr, Int128 val);
-# define HAVE_ATOMIC128 0
#endif
#endif /* HOST_ATOMIC128_LDST_H */
diff --git a/target/s390x/tcg/mem_helper.c b/target/s390x/tcg/mem_helper.c
index bad789a742..db22995171 100644
--- a/target/s390x/tcg/mem_helper.c
+++ b/target/s390x/tcg/mem_helper.c
@@ -1778,7 +1778,7 @@ static uint32_t do_csst(CPUS390XState *env, uint32_t r3,
uint64_t a1,
max = 3;
#endif
if ((HAVE_CMPXCHG128 ? 0 : fc + 2 > max) ||
- (HAVE_ATOMIC128 ? 0 : sc > max)) {
+ (HAVE_ATOMIC128_RW ? 0 : sc > max)) {
cpu_loop_exit_atomic(env_cpu(env), ra);
}
}
--
2.34.1
